It has been previously suggested that the startup procedure for a fuel cell stack at subfreezing temperature is hampered by the presence of ice in the reactant flow fields. The ice prevents the reactant gases from reaching certain parts or even all of the electrodes' catalyst layer surfaces. To avoid such a situation, many proposals have been made for removing all of the water and water vapor from the stack when the stack is being shut down so that there is no possibility of ice being present upon re-establishing operation. Such systems are expensive, awkward, and quite time-consuming, and are certainly not at this time well suited for fuel cell power plants used in vehicles. The dry out of the cell stack assembly which is necessary for good cold start performance, can result in severe membrane stress, leading to untimely membrane failure.
Other approaches to the catalyst/ice problem include all sorts of heating methodologies, which are also expensive, cumbersome, require too much time, and are not well suited for vehicular applications
This modality is predicated on the realization that poor end-cell performance in a fuel cell stack assembly a) during and following boot strap startup at sub-freezing temperatures, and b) resulting from freeze/thaw cycles, is caused by flooding. During start-up from frozen temperatures, the end cells on both the cathode and anode ends of the stack become flooded to the greatest degree.